Taking a widescreen television having a diagonal screen size of 42 inches as an example, a liquid-crystal panel therefor comprises a layered liquid-crystal panel which includes a pair of rectangular-shaped glass substrates each having a size of about 540 to 560 mm in length×about 950 to 970 mm in width×about 0.7 mm (700 μm) in thickness, and a liquid-crystal layer having a thickness of about 5 μm having a transparent electrode, a color filter etc., and sandwiched between the glass substrates, as shown in FIG. 1. Therefore, the thickness of the liquid-crystal panel itself is about 1.4 mm (1400 μm). The liquid-crystal display element is typically produced from a liquid crystal panel by adhesively applying a polarizing composite sheet which is an optically functional film, commonly referred as “a polarizing plate”, to each of front (viewing side) and back (backlight side) sides thereof.
By the way, for a liquid-crystal display element to function, the direction of orientation of liquid-crystal molecules between two substrates and the direction of polarization of the polarizers laminated to the substrates must be set in a particular relation to each other. In liquid-crystal display element technologies, LCDs (Liquid-crystal Display) using a TN (Twisted Nematic) type liquid-crystal were the first to be put into practical use, and then LCDs using a VA (vertical Alignment) type liquid-crystal, an IPS (Inplane Switching) type liquid-crystal etc., were put into practical use. Although a technical explanation is omitted, in an LCD using such TN-type liquid-crystal panel, liquid-crystal molecules are provided between two upper and lower orientation films having respective rubbing directions on the inner surfaces of glass substrates of the liquid-crystal panel whereby the liquid-crystal molecules are twisted by 90 degrees along the optical axis, s that when a voltage is applied, the liquid-crystal molecules are aligned in a direction perpendicular to the orientation films. However, in case where the LCD is designed to allow images as seen from right side of a display screen as those view as seen from left side, the direction of rubbing on the orientation film at the viewing-side must be 45 degrees (the rubbing direction of the other orientation film is 135 degrees). It is therefore necessary that the polarizing sheets made from a continuous polarizing composite film to be laminated respectively on the front and back sides of the liquid-crystal panel must have polarizers respectively oriented in directions inclined by 45 degrees with respect to a lengthwise or transverse direction of the display screen so as to conform to the rubbing directions.
Generally, in manufacturing a liquid-crystal display element, there is provided a continuous optical film laminate comprising a polarizing composite film including a polarizer which has been subjected to an orientation treatment wherein a polarizer base film is stretched in the lengthwise or transverse direction, a protective film laminated on one side of the polarizer, and an adhesive layer provided on the other side of the polarizer which is the side to be attached to the liquid-crystal panel, and a releasable film releasably attached to the adhesive layer. Therefore, in a polarizing sheet for use in producing a liquid-crystal display element of a TN-type liquid-crystal panel, it is required that the optical film laminate is punched or cut into a rectangular-shaped sheet having a long side or a short side determined in accordance with the size of the TN liquid-crystal panel, in such a manner that the long or short side inclined by 45 degrees with respect to the orientation direction of the polarizer produced by the stretching process. This procedure is described in Japanese Laid-Open Patent Publication JP 2003-161935A (Patent Document 1) or Japanese Patent 3616866 B (Patent Document 2), for example. It is needless to mention that the polarizing composite film sheet of such rectangular shape has a width or a short side dimension which is smaller than that of the polarizing composite film.
The punching or cutting the continuous optical film laminate into the rectangular-shaped sheet may be collectively referred as “a method and system for manufacturing individualized sheets” for liquid-crystal display elements and the sheets thus produced as “individualized sheets”. The punching or cutting is made not only through the surface protection film but also through the carrier film which is provided for protecting the exposed surface of the adhesive layer in the polarizing composite film provided in the continuous optical film laminate The sheet of the carrier film thus punched-out or cut together with the other parts of the laminate may be referred as a “separator”, rather than a “carrier film sheet” in the sense that it no longer serves as a transport medium. Thus, the manufacturing process of the liquid-crystal display elements includes the first step of peeling the separator from each of the optical film laminate sheet to have the adhesive layer in the polarizing sheet exposed. Subsequently, the polarizing sheets each having the adhesive layer exposed are conveyed one-by-one by, for example, being transported under a vacuum suction irrespective of whether or not the surface protection films are laminated on the polarizing sheets, to be laminated to respective ones of a plurality of liquid-crystal panels. According to the aforementioned manufacturing process of the liquid-crystal display elements, it has been required that the sheet punched-out or cut from the continuous optical film laminate as described above is in the form of an individualized sheet having four trimmed sides and possesses a certain level of stiffness having a certain resistance to deflection or bend so that it can be transported and laminated without difficulty. In an initial period in the history of manufacturing process of the liquid-crystal display elements, the optical film sheet or a polarizing sheet contained in such optical film sheet has generally been called as “polarizing plate” which is still used as a common name.
In the manufacturing process of TN-type liquid-crystal display elements, a continuous optical film laminate in the form of a roll of continuous web of such laminate which is then unrolled to be punched-out or cut along cutting lines extending in a direction transverse to the feed direction, to thereby form a plurality of optical film laminate sheets. Such optical film laminate sheet also includes a polarizing sheet which is simultaneously formed during the punching process. However, in this case, it is impossible to produce finished liquid-crystal display elements simply by laminating the sheets thus formed in the punching or cutting process to respective ones of a plurality of liquid-crystal panels in a subsequent process. This is because the sheet of the optical film laminate is cut from the web in such a manner that the sheet has a long or short side extending in a direction 45 degrees with respect to the orientation direction of the polarizer which is the longitudinal or stretching direction of the polarizer base film (i.e., with respect to the feed direction of the optical film laminate prior to the punching or cutting process) so that the sheet cannot be laminated to respective ones of the liquid-crystal panels with the orientation as it has been cut from the web. Therefore, in an effort to provide a finished liquid-crystal display element by transporting a polarizing sheet to a position for lamination with a liquid-crystal panel, and then laminating the polarizing sheet to the liquid-crystal panel, a continuous optical film laminate having a width greater than the long side of the liquid-crystal panel is provided in the form of a roll which is then unrolled in the lengthwise direction. The length of the unrolled optical film laminate is then cut into sheets with their sides oriented in the direction of 45 degrees with respect to the lengthwise direction, using, for example, a die to form a plurality of individual polarizing sheets, which are then appropriately fed to the lamination station where the polarizing sheets are laminated with the liquid-crystal panels, as illustrated and described in the Patent Document 1 or 2. Alternatively, liquid-crystal display elements have been produced with a manufacturing method wherein an elongated optical film laminate is provided from a continuous optical film laminate having a substantially large width by cutting or slitting the continuous optical film laminate in a direction 45 degrees with respect to the lengthwise direction, the elongated optical film laminate having a length corresponding to the widths for a plurality of liquid-crystal display elements. According to another proposal, a plurality of individual sheets are connected into a continuous film configuration to provide an elongated optical film laminate having the orientation direction in 45 degrees with respect to the lengthwise direction of the elongated optical film laminate. Such methods are illustrated and described in Japanese Patent Publication No. 62-14810B (Patent Document 3) and Japanese Patent Publication No. 55-120005A (Patent Document 4). According to the methods, the elongated optical film laminate generally has a width corresponding to that of the liquid-crystal panel and is used by being wound into a roll. The elongated optical film laminate is then taken out from the roll, and cut into a plurality of sheets having required length by slitting the film in the transverse direction with respect to its feed direction. The sheets thus formed are then laminated on the respective ones of liquid-crystal panels sequentially transferred to the laminating station. At any rate, the above methods do not provide any noticeable improvement over the method of using individualized separate sheets of polarizers in manufacturing TN-type liquid-crystal display elements.
The Patent Document 3 is a Japanese Patent Publication No. 62-14810B which discloses an apparatus to produce a liquid-crystal panel by sequentially laminating a plurality of sheets each having a required length to respective ones of a plurality of liquid-crystal panels while continuously feeding a continuous optical film laminate containing a polarizing composite film, before the VA-type liquid-crystal and the IPS-type liquid-crystal are brought into practical use. According to the method disclosed by the Patent Document 3, a continuous optical film laminate is provided. The continuous optical film laminate comprises a polarizing composite film of a substantial length (in the Patent Document 3, termed as an “elongated polarizing plate”) and a separator for protecting an adhesive layer provided on one side of the polarizing composite film and supplied in the form of a roll. The continuous optical film laminate is then unrolled from the roll of the film laminate and subjected to a process of “slitting only the polarizing plate 4 and the adhesive layer 5 while leaving the separator 6 uncut (hereinafter referred as “half-cut”)” to thereby form polarizing sheets of desired dimensions. If it is found that anyone of the polarizing sheets contain a defect or defects, such defective polarizing sheet is removed from the process line in the course of the unrolling process. The polarizing film having no defect or defects are then peeled off the separator and sequentially laminated the liquid-crystal panels (in the Patent Document 3, termed as “liquid-crystal cells”). It is interpreted that the method is proposed specifically for manufacturing small-size display screens for use with electronic calculators or the like. The method can produce “products each having the polarizing composite film and the liquid-crystal cell laminated together”. The apparatus is considered to be a type of labeler unit which produces an LCD using the TN-type liquid-crystal. There is taught to produce the optical film laminate in the form of an elongated sheet, and for the purpose, an optical film laminate having a substantially large width is provided and slit in a direction 45 degrees oblique to the longitudinal direction of the optical film laminate with a width corresponding to the width of the liquid-crystal panel. Alternatively, a film-like elongated optical film laminate sheet may be formed by longitudinally connecting a plurality of optical film laminate sheets. Therefore, this apparatus is based on the use of an elongated polarizing sheet which is cut in a direction 45 degrees oblique to the stretching direction of the polarizing composite film with a width corresponding to the width of the liquid-crystal panel. Therefore, the method taught by the Patent Document 3 cannot be applied directly to a manufacturing process adapted to perform steps of continuously providing a plurality of polarizing sheets from a continuous optical film laminate and then laminating the respective polarizing sheets to respective ones of the liquid-crystal panels comprising VA-type or IPS-type liquid-crystal to produce liquid-crystal display elements.
The Patent Document 4 is a Japanese Patent Publication No. 55-120005A which discloses an apparatus based on the technology developed before the VA-type liquid-crystal and the IPS-type liquid-crystal are brought into practical use as in the case of the Patent Document 3. According to the teachings in the Patent Document 4, a liquid-crystal display element is produced by sequentially laminating a plurality of sheets of optical film laminate comprising a polarizing composite film each having a required length to respective ones of a plurality of liquid-crystal panels. A length of the optical film laminate is supplied in the form of a roll, and continuously unrolled for use in the process. The optical film laminate is produced from a polarizing composite film having a substantial width by applying an adhesive layer on one side of the composite film. A plurality of elongated polarizing composite film sheets having a required width are then provided by cutting the polarizing composite film. These sheets are then applied to a separately prepared conveyance medium (i.e., a carrier film) which has preliminarily been subjected to a releasing treatment to produce an optical film laminate. Then, the optical film laminate is subjected to a half-cut process in a transverse direction by means of two knives which are spaced apart by a required distance in the longitudinal direction, leaving the conveyance medium uncut. Thus, the optical film laminate is sequentially cut into a plurality of sheets on the conveyance medium, and the plurality of formed sheets are sequentially laminated to respective ones of the liquid-crystal panels being conveyed to manufacture the liquid-crystal display element. This apparatus is also based on the use of an elongated polarizing sheet which is cut in a direction 45 degrees oblique to the stretching direction of the polarizing composite film with a width corresponding to the width of the liquid-crystal panel. Therefore, the technology disclosed by the Patent Document 4 cannot be applied directly to a manufacturing apparatus adapted to perform steps of continuously forming a plurality of polarizing sheets from a continuous optical film laminate and laminating respective sheets to respective ones of the liquid-crystal panels comprising VA-type or IPS-type liquid-crystal to produce liquid-crystal display elements.
With respect to automation of manufacturing process for liquid-crystal display elements using individualized polarizing sheets will generally be described below. First, a plurality of rectangular individualized sheets are formed from a continuous optical film laminate containing a polarizing composite film and preliminarily subjected to inspection for the presence or absence of any defect in an optical film laminate manufacturing line. The formed individualized sheets inspected for the presence of defects are transported to a liquid-crystal display element manufacturing line in a batch. Generally, the carried-in individualized sheets are manually stored in a polarizing-sheet magazine. Each of the stored individualized sheets has a polarizing sheet comprising at least an adhesive layer and a separator laminated thereto to protect the exposed part of the adhesive layer. The magazine storing the individualized sheets is introduced into the liquid-crystal display element manufacturing line. There is provided a liquid-crystal panel magazine which is incorporated in the same manufacturing line and stores a plurality of liquid-crystal panels. A plurality of liquid-crystal panels are taken out one-by-one from the liquid-crystal panel magazine and conveyed through a cleaning/polishing station. In synchronization with the conveyance of the liquid-crystal panels, the individualized polarizing sheets are taken out one-by-one from the individualized-sheet magazine by means of a suction conveying unit. The separator is then peeled from each of the taken-out individualized sheets to expose the adhesive layer of the sheet. When producing a liquid-crystal display element using the individualized sheet in this manner, the separator must be removed from respective ones of the individualized sheets one-by-one. Then, the individualized sheets with the adhesive layer exposed are carried under suction to the lamination station to be laminated to the liquid-crystal panel. Each of the transported individualized sheets is laminated to one side of the liquid-crystal panel to sequentially produce the liquid-crystal display elements. This method is disclosed, for example, in Japanese Laid-Open Patent Publication No. 2002-23151A (Patent Document 5). Flexible individualized sheets tend to be bowed or warped due to curves or distortion of its edge, and thus it is a serious technical impediment to accuracy and speed in registration and lamination with liquid-crystal panels. Thus, it will be understood that the individualized sheet is required to have a certain level of thickness and stiffness to facilitate registration and lamination with liquid-crystal panels typically in transportation under suction. For example, the disclosures in the Japanese Laid-Open Patent Publication No. 2004-144913A (Patent Document 6), Japanese Laid-Open Patent Publication No. 2005-298208A (Patent Document 7) or Japanese Laid-Open Patent Publication No. 2006-58411A (Patent Document 8) can be considered as measures addressing such technical problems.
On the other hand, the VA-type and IPS-type liquid-crystal panels are not designed to arrange liquid-crystal molecules in twisted orientations. Thus, when producing liquid-crystal display element using these types of liquid-crystal panels, there is no need to have the polarization axis of the polarizing sheet oriented 45 degrees with respect to the direction of the long or short side of the liquid-crystal display element in view of viewing angle characteristics inherent to the orientation of the liquid-crystal, as having been required when using the TN-type liquid-crystal panel. Each of these liquid-crystal display elements using these liquid-crystal panels is formed by applying sheets to the opposite sides of the liquid-crystal display panel oriented with their polarization axes crossed at 90 degrees crossing angle. In the case of the VA-type and IPS-type liquid-crystal panels, with respect to the viewing angle characteristics, maximum contrast can be obtained along the direction of the polarizing axis of the polarizing sheet, so that it is preferable that the sheets have polarizing axes oriented in parallel with the longitudinal or transverse direction of the liquid-crystal panel from the technical view point of symmetry of the viewing angle characteristics and visibility. Thus, it will be understood that these sheets to be applied to the liquid-crystal panel has a feature that the continuous optical film laminate including a polarizing composite film which has been subjected to a longitudinal or transverse stretching can be continuously fed out from a roll and cut along transverse lines with respect to the feed direction of the optical film laminate to sequentially produce rectangular polarizing sheets including the polarizing sheets having the same width as the optical film laminate width.
It should further be pointed out that, from the view point of improving the viewing angle characteristics, there is a trend that, for liquid-crystal used in a display element for widescreen televisions, the VA-type liquid-crystal or the IPS-type liquid-crystal are more widely adopted than the TN type. As described, the conventional display element using the TN-type liquid-crystal had to be manufactured using the individualized sheets. Due to limitations in both product accuracy and manufacturing speed, it is difficult to enhance the manufacturing efficiency in this method anymore. In view of such trend in environments of technical developments, there has been made a proposal such as the one described in Japanese Laid-Open Patent Publication No. 2004-361741A (Patent Document 9) which is based on use of the VA-type or IPS-type liquid-crystal panels and comprises steps of continuously feeding an optical film laminate comprising a polarizing composite film, slitting the optical film laminate in conformity to the size of a liquid-crystal panel and sequentially laminating a plurality of sheets which have been produced by the slitting step to respective ones of a plurality of the liquid-crystal panels.
The subjects and the concepts of the present invention are close to and inseparably linked with the manufacture of a liquid-crystal display element using a liquid-crystal such as the VA-type and IPS-type liquid-crystals which are different in principle from the TN-type liquid-crystal, as described later.
However, the mainstream of manufacture of liquid-crystal display elements is still based on the manufacturing technology utilizing individualized sheets, due to the following technical problems. In manufacturing liquid-crystal display elements, a critical technical challenge is to detect any defect which may otherwise be retained in the display elements to be formed, and to prevent any defective product from being produced. This makes it possible to significantly improve manufacturing yield. Most of the product defects primarily arise from defects in the polarizing composite film contained in the optical film laminate. However, it is not actually a practical way to provide a continuous optical film laminate after completely removing all defects contained in individual films which are to be laminated together to form the optical film laminate. An observation for defects in the polarizing composite film on all of the polarizer and the protective film laminated on the polarizer to provide a polarizing composite film having no adhesive layer formed thereon, and an adhesive layer formed on the polarizing composite film has revealed that there are various kinds of defects, including defects inherent in the PVA film of the polarizer itself, defects arose in connection with the lamination of the protective film to the polarizer and defects generated in the adhesive layer of the formed polarizing composite film, distributed in 20 to 200 positions over a unit length of the polarizing composite film of 1000 m. Thus, it is extremely difficult to produce a defect-free optical film laminate under existing circumstances. Nonetheless, in view of maintaining quality of a display element itself, it is not permitted to use a polarizing composite film sheet having visible flaws or defects as a sheet for television display element even if such a flaw or defect is small. Given that the long side dimension of a polarizing sheet formed from the polarizing composite film is about 1 m, if a defective region cannot be preliminarily removed, 20 to 200 defective liquid-crystal display elements out of 1,000 products will be produced according to a simple calculation.
Thus, under the existing circumstances, it has only been possible to define defect-free regions and defect-containing regions in the polarizing composite film as rectangular regions of the same shape and size, and defect-free polarizing sheets (hereinafter referred as “normal polarizing sheets”) are then cut from the polarizing composite film, appropriately avoiding defect-containing regions to have the normal polarizing sheets laminated to the respective ones of the liquid-crystal panels as a rectangular-shaped normal polarizing sheet in the later process. The defect-containing regions are also cut from the polarizing composite film, as defective polarizing sheets (hereinafter referred as “defective polarizing sheets”), and the rectangular shaped defective polarizing sheets can only be removed selectively in the later process.
Proposals relating to a preliminary inspection apparatus for a polarizing composite film have previously been made, as disclosed, for example, in Japanese Patent No. 3974400B (Patent Document 10), Japanese Laid-Open Patent Publications 2005-62165A (Patent Document 11) and 2007-64989A (Patent Document 12). These proposals relate to method based on the use of individualized sheets, and primarily includes the steps of inspecting defects in a web of a polarizing composite film being continuously fed to determine positions or coordinates of detected defects, if any, through image processing, encoding information obtained by the image processing, directly printing the encoded information on marginal or edge portion of the polarizing composite film which will be left in the web after cutting the polarizing composite film during the production of the individualized sheets, and taking up the resulting polarizing composite film to form a roll. The method further comprises the steps of reading the encoded information printed on the polarizing composite film fed out of the roll, providing marks at the positions of the defects based on the results of determination on the presence of defects, cutting the polarizing composite film for producing individualized sheets, and based on the marks provided beforehand, sorting the individualized sheets into normal and defect-containing products. The above steps have been believed as being essential to improving yield in the manufacture of such individualized sheets.
Just for reference, in the Patent Document 10 or 12, the polarizing composite film is termed as “sheet-shaped member”, and there is described that the sheet-shaped member may include “for example, a polarizing composite film, a phase difference film, an plastic sheet for organic electroluminescent (EL) elements, a plastic sheet for liquid-crystal cells, and a plastic sheet for solar battery boards”. In an example illustrated in FIGS. 1 (a) and 1 (b) of the Patent Document 10 or 12, the sheet-shaped member includes a polarizing composite film, which has a polarizer and two protective films laminated to respective ones of the opposite surfaces of the polarizer, and there is described that the polarizing composite is punched out or cut into sheets and the resultant sheet is termed as “product”. In the Patent Document 11, the polarizing composite film is termed as a “polarizing plate stock”, and a cut piece is termed as a “sheet-shaped product”. The Patent Documents 10 or 12 first describes a method wherein an inspection unit is used to detect defects present in the polarizing composite film in terms of positions or coordinates locations of the defects. Then the detected information is encoded. The encoded information is printed by a recording device to print onto a polarizing composite film. The encoded information is printed onto appropriated positions of the polarizing composite film in such a manner as to be readable by a reading unit when a sheet is cut from the polarizing composite film. The polarizing composite film having the encoded information printed thereon is wound into a roll. The Patent Documents 10 to 12 also disclose a further manufacturing step wherein the roll produced in the first process is transformed into separate sheets of polarizing film by unrolling the polarizing composite film from the roll and forming sheets from the polarizing composite film. The manufacturing process further comprises a first sub-step of making a mark directly to a position or coordinate location of a defect of the polarizing composite film, based on the encoded information on the polarizing composite film and read by the reading unit, and a second sub-step of punching or slitting the polarizing composite film being fed out from the roll, and allowing the polarizing sheet punched out or cut from the polarizing composite film fed out from the roll to be sorted into a normal product and a defective product in the next process according to the presence or absence of marks.
It should be noted that there is a significant difference in the surrounding circumstances between the conventional technique where a plurality of individualized sheets are preliminarily formed from a continuous optical film laminate, and then transported in a batch into the manufacturing process of the liquid-crystal display element for lamination on respective ones of a plurality of liquid-crystal panels one-by-one, and a continuous manufacturing of liquid-crystal display elements that the present invention is aiming at, where only the sheets that are determined to be normal sheets are supplied to a lamination station to be laminated to the liquid-crystal panels, while unrolling a continuous optical film laminate with predefined slit lines, without interrupting the feed of the optical film laminate with slit lines, by providing a measure to keep the polarizing sheets, which are determined to be the defective polarizing sheet out of the normal polarizing sheets and the defective polarizing sheets that are sequentially formed separated from each other on the carrier film, from being laminated to the liquid-crystal panel, as described later.
For preventing the defective polarizing sheet of the polarizing composite film from being transported to the lamination station for lamination with liquid-crystal panels, it is generally a preferable way that in unrolling the continuous optical film laminate comprising the polarizing composite film, defective regions of the polarizing composite film are cut from the continuous optical film laminate as the defective polarizing sheet and removed from the manufacturing line. With this process, the feed of the continuous optical film laminate may be interrupted. If the defective regions of the polarizing composite film are left as they are in order to avoid interruption of the feed of the continuous optical film laminate, it becomes difficult to avoid defective liquid-crystal display elements being formed. Even though a manufacturing speed can be maintained, it is compelled to sacrifice product yield. This is one of the technical problems to be solved by the present invention. Specifically, the problem is how to remove the defective region or defective polarizing sheets of the polarizing composite film included in the continuous optical film laminate in the process of the feed of the continuous optical film laminate without interrupting the feed.
The applicant has already proposed a manufacturing method by the Japanese Laid-Open Patent Publication 2007-140046A (Patent Document 13) wherein the method comprises the steps of peeling a carrier film from a continuous optical film laminate unrolled continuously from a roll of the continuous optical film laminate to expose a polarizing composite film having an adhesive layer, inspecting a defect or defects present in the polarizing composite film, punching or cutting only normal regions of a polarizing composite film into a rectangular shape, while leaving the defective region or regions of the polarizing composite film in the place, and transporting the resulting normal polarizing sheet to a lamination position using another conveyance medium. It should however be noted that this process is not the one which makes it possible to feed only the normal polarizing sheets produced from the continuous optical film laminate to the lamination station with the liquid-crystal panel by means of the carrier film. This technique is a method where the plurality of cut and individualized sheets are releasably laminated to another conveyance medium and transported to the lamination station with the liquid-crystal panel, which is similar to the method where the polarizing composite film is cut on separately provided conveyance medium, and the sheet is transported to the lamination station with the liquid-crystal panel, disclosed in Patent Document 4. It should be referred that this technique is not beyond the individualized sheet manufacturing system of the liquid-crystal display elements.
The applicant has further disclosed by the Japanese Patent Application No. 2007-266200 an invention relating to a method and a system for laminating a polarizing sheet to a liquid-crystal panel, as shown in FIG. 2. This is a method and system for manufacturing liquid-crystal display elements comprising the steps of peeling a first carrier film which is provided for protecting the adhesive layer of a polarizing composite film contained in the continuous optical film laminate preliminarily inspecting a defect or defects present in the continuous polarizing composite film having the adhesive layer exposed by peeling the first carrier film, feeding a second carrier film and releasably laminating the second carrier film to the exposed adhesive layer of the polarizing composite film to provide again a protection for the adhesive layer. Therefore, it is possible to inspect a defect or defects present in the polarizing composite film during the feeding operation of the continuous optical film laminate without interrupting the feed. Then, this method further comprises a step of forming a plurality of slit lines in the continuous optical film laminate along a direction transverse to the feed direction of the optical film laminate, the slit lines being formed to a depth reaching the inner surface of the second carrier film to thereby define defect-containing polarizing sheets and defect-free, normal non-defective polarizing sheets between respective longitudinally adjacent two slit lines formed sequentially on the optical film laminate along the feed direction, while the defective polarizing sheet and the defect-free, normal polarizing sheet respectively corresponds to a defective region including defects and normal region including no defect of the polarizing composite film segmented into a plurality of rectangular shape as determined by the result of the inspection for the existence of defects in the polarizing composite film. This method also comprises a step of automatically removing only the defective polarizing sheets from the second carrier film and feeding only the normal polarizing sheets left on the second carrier film to a lamination station. Finally, the method comprises the step of peeling the normal polarizing sheets from the second carrier film, and laminating each of the normal polarizing sheets to one of opposite surfaces of each of the liquid-crystal panels. This method contains an innovative proposal allowing for shifting from a conventional liquid-crystal display element manufacturing system which is designed to carry a plurality of preliminarily formed individualized sheets in a batch in the manufacturing process of the liquid-crystal display element, and laminate the individualized sheets one by one to respective ones of a plurality of liquid-crystal panels, to a continuous manufacturing system for liquid-crystal display element designed to continuously form a plurality of polarizing sheets from a continuous optical film laminate fed out from a roll, and directly laminate the formed sheets to respective ones of a plurality of liquid-crystal panels. The roll of the continuous optical film laminate used in the above method is a roll of the continuous optical film laminate that comprises a polarizing composite film having an adhesive layer which at least is not preliminarily inspected and a carrier film that is releasably laminated on the adhesive layer.
The technical challenge of the aforementioned method and apparatus shown in FIG. 2 of the Patent Application No. 2007-266200 has been how to realize the technical measures for forming a plurality of slit lines in the continuous optical film laminate in a direction transverse to the feed direction of the continuous optical film laminate at a side opposite to the second carrier film to a depth reaching the adhesive surface of the second carrier film, during the feed of the continuous optical film laminate, to form defective polarizing sheets and normal polarizing sheets, between respective two of the slit lines formed sequentially along the feed direction, the defective polarizing sheets and the normal polarizing sheets respectively corresponding to the preliminarily defined defective and defect-free regions in the polarizing composite film as determined by the result of the inspection for the existence of a defect or defects in the polarizing composite film, while preventing only the defective polarizing sheets from being transported to the lamination position for lamination with the liquid-crystal panel. As a result, the technical challenge has been solved by providing steps of, for the inspection for defining the defective and defect-free regions, separating the continuous optical film laminate from the carrier film and/or the surface-protection film, and after the inspection, laminating a substitute carrier film and/or a surface protection film again on the continuous optical film laminate, these steps being and incorporated as a series in the manufacturing process of the liquid-crystal display element. These steps have made it possible to inspect defects in the polarizing composite film during the manufacturing process of the liquid-crystal display elements by separating the carrier film and/or the surface protection film from the continuous optical film laminate comprising the polarizing composite film and exposing the polarizing composite film having the adhesive layer. It should be noted that these steps are essential to protect the surface opposite to the adhesive layer of the polarizing composite film and the exposed surface of the adhesive layer of the polarizing composite film. However, although these steps are essential, the steps cause not only substantial complexity in the entire system for laminating the normal polarizing sheets of the formed polarizing composite film to corresponding ones of the liquid-crystal panels but also an increase in the number of steps and difficulty in control for each step, and as a matter of course, cause corresponding reduction in the manufacturing speed.
The present invention has been made based on the aforementioned prior proposals and through intensive researches and considerations for significantly enhancing product accuracy and manufacturing speed, and drastically improving manufacturing yield, in the manufacture of liquid-crystal display elements.
The prior art documents referred to in the above descriptions are listed below.                Patent Document 1: Japanese Laid-Open Patent Publication 2003-161935A        Patent Document 2: Japanese Patent No. 3616866B        Patent Document 3: Japanese Patent Publication 62-14810B        Patent Document 4: Japanese Laid-Open Patent Publication 55-120005A        Patent Document 5: Japanese Laid-Open Patent Publication 2002-23151A        Patent Document 6: Japanese Laid-Open Patent Publication 2004-144913A        Patent Document 7: Japanese Laid-Open Patent Publication 2005-298208A        Patent Document 8: Japanese Laid-Open Patent Publication 2006-58411A        Patent Document 9: Japanese Laid-Open Patent Publication 2004-361741A        Patent Document 10: Japanese Patent No. 3974400B        Patent Document 11: Japanese Laid-Open Patent Publication 2005-62165A        Patent Document 12: Japanese Laid-Open Patent Publication 2007-64989A        Patent Document 13: Japanese Laid-Open Patent Publication 2007-140046A        